This invention relates to catheters, and more particularly to percutaneous transluminal laser catheters.
The use of angioplasty catheters for treating occlusions in blood vessels, particularly in arteries, is well known. Typically such a catheter is equipped with an inflatable balloon near its distal or forward tip. A more recent technique involves providing an optical fiber in the catheter, and extending the distal end of the fiber slightly beyond the distal tip of the catheter, whereby laser energy generated at the proximal end of the fiber is transmitted to an occlusion to be treated. For a further explanation of this technique, reference is made to U.S. patent application Ser. No. 679,633, filed Dec. 10, 1984, now U.S. Pat. No. 4,669,465 and U.S. patent application Ser. No. 887,196, filed July 12, 1986, sending both assigned to the assignee of this application. The proper positioning and orientation of the catheter distal tip is vital to the success of this technique. Precise positioning is essential to ensure that laser energy from the optical fiber is directed onto the occlusion rather than onto the arterial wall. Improper aiming can lead to damage of the wall or, in severe cases, rupture the artery.
Apparatus for positioning a catheter distal tip is known, although not necessarily in connection with transmission of laser energy in a catheter. For example, U.S. Pat. No. 4,582,181 to Samson granted Apr. 15, 1986 shows a dilating catheter inserted into a guide catheter. A flexible helical coil at the catheter distal end can be steered using a knob at the catheter proximal end. Once the catheter is positioned, a balloon near its distal tip is inflated. U.S. patent application Ser. No. 041,996, filed Apr. 24, 1987, pending and assigned to the present assignee, describes a catheter balloon having a blunt forward end particularly well suited for centering the distal tip of a catheter tube.
Further patents disclose placement of an inflatable balloon at or beyond the distal end of the catheter tubing, although not in connection with a laser enhanced angioplasty catheter. For example, U.S. Pat. No. 4,531,943 to Van Tassel et al discloses an inflatable, non-distensible balloon forming a somewhat toroidal distal tip when inflated. The catheter includes a central lumen for supplying fluids to an opening formed by the balloon. A separate balloon inflation lumen is provided to inflate the balloon. U.S. Pat. No. 4,029,104 to Kerber discloses a calibrated leak balloon catheter, in which a balloon is fastened to the outside distal end region of a catheter tube. A discharge orifice is provided through a plug mounted at the distal end of the balloon. While the devices disclosed in these two patents are suitable for particular purposes, they fall short of the need for precise catheter tip positioning in laser enhanced catheters.
Therefore, it is an object of the present invention to provide a means for accurately setting the position and orientation of the distal end of a laser catheter when it is inserted into an artery or other vessel.
Another object of the invention is to provide an inflatable tip for a laser catheter, which tip is particularly well adapted for centering and aiming an optical fiber housed in the catheter.
Yet another object of the invention is to provide improved centering accuracy in a transluminal laser catheter by minimizing the axial extension of the optical fiber distally of the catheter tip feature which locates the optical fiber lumen with respect to the artery being treated.